Data: 2023 USDA zones (PRISM/OSU) · NOAA 1991–2020 normals · updated Oct 29, 2026

Planting zone for 99026 — Nine Mile Falls, WA

ZIP code 99026 (Nine Mile Falls, Spokane County) is in USDA zone 6b: the coldest winter night averages −5 to 0 °F. The median last spring frost is May 10 and the first fall frost September 26.

Where ZIP 99026 is

Outlined: the ZIP code area · tap the map for the zone at any spot · scroll or pinch to zoom

Not the official USDA Plant Hardiness Zone Map. Zones come from the 2023 USDA hardiness-zone data by the PRISM Group, Oregon State University; we re-mapped and recolored them. The official map is at planthardiness.ars.usda.gov.

Zone6b−5 to 0 °F

Coldest night−20.6 to −17.8 °C

Last frostMay 10

First frostSep 26

2012 zone6a

Was 6a on the 2012 map — half a zone warmer now. The zone is the one at the center of the ZIP code; hilly ZIPs can span two zones. What zone 6b means →

Frost forecast — next 7 nights

live from the National Weather Service

Loading the forecast for Nine Mile Falls, WA…

Forecast data: National Weather Service (api.weather.gov), public domain. This is not a warning service — for official frost and freeze warnings see weather.gov.

Frost dates in Nine Mile Falls, WA

JanFebMarAprMayJunJulAugSepOctNovDec

Blue: frost possible · fading green: frost risk falling or rising (90% → 10%) · green: frost-free

Last spring frostMay 10median — 50% chance of a later frost

Safe for tender plantsMay 30only 10% chance of frost after

First fall frostSeptember 26median — 10% chance by Sep 11

Growing season137 daysfrost-free, median

A hard freeze (28 °F) usually ends around April 25 and returns around October 7.

From the NOAA station Spokane WFO, WA — 8 miles away, elevation 2,392 ft. NOAA NCEI U.S. Climate Normals 1991–2020, 32 °F threshold. Low spots and valleys can freeze later in spring than the station.

When to plant vegetables in 99026

JanFebMarAprMayJunJulAugSepOctNovDec

PeasSow outdoors · Mar 29 – Apr 12

SpinachSow outdoors · Mar 29 – Apr 19

Broccoli, cabbageStart indoors · Mar 1 – Mar 15

Broccoli, cabbageTransplant · Apr 19 – May 3

Onion setsPlant outdoors · Apr 12 – Apr 26

PotatoesPlant outdoors · Apr 19 – May 3

LettuceSow outdoors · Apr 12 – Apr 26

Carrots, beetsSow outdoors · Apr 19 – May 3

TomatoesStart indoors · Mar 15 – Mar 29

TomatoesTransplant · May 17 – May 31

Peppers, eggplantStart indoors · Mar 1 – Mar 15

Peppers, eggplantTransplant · May 24 – Jun 7

BeansSow outdoors · May 17 – May 31

Sweet cornSow outdoors · May 17 – May 31

Cucumbers, squashSow outdoors · May 17 – May 31

Fall lettuce, spinachSow outdoors · Aug 1 – Aug 15

GarlicPlant cloves · Sep 12 – Oct 17

Start seeds indoorsSow or plant outdoorsFall plantingMedian last & first frost

Counted from the median last spring frost (May 10) and first fall frost (Sep 26) with the rules of thumb U.S. extension services publish. Cool-season crops take a light frost; warm-season crops do best once the soil is above about 60 °F.

When spring arrived in 2026

In 2026, spring leaf-out near 99026 came on Apr 2 — 4 days earlier than the 1991–2020 average (Apr 6).

average
Apr 62026
Apr 2

JanFebMarAprMayJun

The Spring Index marks the day when accumulated warmth is enough for lilac and honeysuckle to leaf out — a widely used signal that the growing season has started. Source: USA National Phenology Network, www.usanpn.org — Spring Indices, first leaf, 2026 (data as of 2026-09-08) and 30-year average 1991–2020 (CC BY 4.0).

Native plants for zone 6b in Washington

581 plants native to the lower 48 states, recorded in Washington, and rated by the USDA to survive −5 °F or colder — the bottom of zone 6b. Each links to its USDA PLANTS profile.

Source: USDA, NRCS. 2026. The PLANTS Database (plants.usda.gov), National Plant Data Team — state distribution, native status and the “Temperature, Minimum” characteristic. Check light, moisture and soil needs before buying; local nurseries and your state native plant society can confirm what thrives in Nine Mile Falls, WA.

Soil in Nine Mile Falls, WA

The soil mapped at the center of ZIP 99026 is Springdale — slightly decomposed plant material, somewhat excessively drained.

TextureSlightly decomposed plant materialtop layer

pH5.0strongly acidic; most vegetables like 6.0–7.0

DrainageSomewhat excessively drainednatural drainage class

Organic matter75%high

Hydrologic groupAwater soaks in fast

Farmland classPrime farmland if irrigatedUSDA classification

Map unit: Springdale gravelly ashy coarse sandy loam, 0 to 8 percent slopes.

Soil Survey Staff, Natural Resources Conservation Service, USDA. Soil Survey Geographic (SSURGO) Database, via Soil Data Access, accessed 2026-10-29. The soil at the center point of ZIP 99026; soils change within a few hundred feet, so a home soil test (pH, nutrients) is still the best guide.

Climate in Nine Mile Falls, WA

Summer high83 °Faverage high, July

Winter low22 °Faverage low, December

Hot days20days a year at 90 °F or more

Freezing nights157nights a year at 32 °F or less

Growing degree days1,843base 50 °F — the season’s usable heat

Longest day16 h 01 mindaylight on June 21

Shortest day8 h 24 mindaylight on December 21

Onions to growLong-daysummer days reach 15+ hours, enough for long-day varieties (intermediate types work too)

Precipitation17.4 inper year, rain and melted snow

Snowfall48 inper year; 56 days with snow on the ground

Average high and low, by month

Precipitation by month inches · ❄ = snowfall

NOAA NCEI U.S. Climate Normals 1991–2020 — temperature: Spokane WFO, WA (8 mi away); precipitation: Spokane WFO, WA (8 mi away). Daylight is calculated from latitude.

Nearby ZIP codes

2 of the 8 nearest ZIP codes are in a different zone — elevation and distance from water change winter lows quickly.

Airway Heights, WA · 11 mi

992246b

Spokane, WA · 12 mi

Washington planting zones →

Questions about 99026

What planting zone is ZIP code 99026?

ZIP code 99026 (Nine Mile Falls, WA) is in USDA hardiness zone 6b on the 2023 map: the coldest night of an average winter reaches −5 to 0 °F (−20.6 to −17.8 °C).

When is the last frost in Nine Mile Falls, WA?

The median last spring frost (32 °F) near 99026 is May 10; after May 30 there is only a 10% chance of frost. Data: NOAA 1991–2020 normals, Spokane WFO station.

When is the first frost in Nine Mile Falls, WA?

The median first fall frost near 99026 is September 26, giving a median frost-free growing season of 137 days.

When should I plant tomatoes in 99026?

Start tomato seeds indoors around Mar 15 – Mar 29 and set transplants outside around May 17 – May 31, one to three weeks after the median last frost.

How much rain and snow does 99026 get?

About 17.4 inches of precipitation a year and 48 inches of snowfall (NOAA 1991–2020 normals, Spokane WFO station).

How hot do summers get in Nine Mile Falls, WA?

The average high peaks at 83 °F in July, with about 20 days a year at 90 °F or more.

What kind of soil does 99026 have?

The USDA soil survey maps Springdale at the center of ZIP 99026: slightly decomposed plant material, somewhat excessively drained, pH about 5.0 (strongly acidic).

Did spring come early in Nine Mile Falls, WA in 2026?

Spring leaf-out near 99026 came on Apr 2 in 2026, 4 days earlier than the 1991–2020 average (Apr 6), according to the USA National Phenology Network Spring Index.

What kind of onions grow in Nine Mile Falls, WA?

Long-day onions: the longest day near 99026 is 16 h 01 min, so summer days reach 15+ hours, enough for long-day varieties (intermediate types work too).

Did the zone for 99026 change?

Yes. The 2012 USDA map put 99026 in zone 6a; the 2023 map puts it in zone 6b. The newer map uses 1991–2020 data and more weather stations.